[FFmpeg-devel] [PATCH] avcodec: add HDMV Text Subtitle decoder

wm4 nfxjfg at googlemail.com
Tue Jan 31 17:42:54 EET 2017


On Tue, 31 Jan 2017 15:22:17 +0100
Paul B Mahol <onemda at gmail.com> wrote:

> Signed-off-by: Paul B Mahol <onemda at gmail.com>
> ---
>  libavcodec/Makefile        |   2 +
>  libavcodec/allcodecs.c     |   2 +
>  libavcodec/textst_parser.c |  49 ++++++++++++++++++++
>  libavcodec/textstdec.c     | 108 +++++++++++++++++++++++++++++++++++++++++++++
>  libavformat/utils.c        |   1 +
>  5 files changed, 162 insertions(+)
>  create mode 100644 libavcodec/textst_parser.c
>  create mode 100644 libavcodec/textstdec.c
> 
> diff --git a/libavcodec/Makefile b/libavcodec/Makefile
> index 43a6add..edadb0f 100644
> --- a/libavcodec/Makefile
> +++ b/libavcodec/Makefile
> @@ -539,6 +539,7 @@ OBJS-$(CONFIG_SVQ1_ENCODER)            += svq1enc.o svq1.o  h263data.o  \
>  OBJS-$(CONFIG_SVQ3_DECODER)            += svq3.o svq13.o mpegutils.o h264data.o
>  OBJS-$(CONFIG_TEXT_DECODER)            += textdec.o ass.o
>  OBJS-$(CONFIG_TEXT_ENCODER)            += srtenc.o ass_split.o
> +OBJS-$(CONFIG_TEXTST_DECODER)          += textstdec.o ass.o
>  OBJS-$(CONFIG_TAK_DECODER)             += takdec.o tak.o takdsp.o
>  OBJS-$(CONFIG_TARGA_DECODER)           += targa.o
>  OBJS-$(CONFIG_TARGA_ENCODER)           += targaenc.o rle.o
> @@ -945,6 +946,7 @@ OBJS-$(CONFIG_RV30_PARSER)             += rv34_parser.o
>  OBJS-$(CONFIG_RV40_PARSER)             += rv34_parser.o
>  OBJS-$(CONFIG_SIPR_PARSER)             += sipr_parser.o
>  OBJS-$(CONFIG_TAK_PARSER)              += tak_parser.o tak.o
> +OBJS-$(CONFIG_TEXTST_PARSER)           += textst_parser.o
>  OBJS-$(CONFIG_VC1_PARSER)              += vc1_parser.o vc1.o vc1data.o  \
>                                            simple_idct.o wmv2data.o
>  OBJS-$(CONFIG_VP3_PARSER)              += vp3_parser.o
> diff --git a/libavcodec/allcodecs.c b/libavcodec/allcodecs.c
> index f92b2b7..9a90533 100644
> --- a/libavcodec/allcodecs.c
> +++ b/libavcodec/allcodecs.c
> @@ -581,6 +581,7 @@ void avcodec_register_all(void)
>      REGISTER_DECODER(SUBVIEWER,         subviewer);
>      REGISTER_DECODER(SUBVIEWER1,        subviewer1);
>      REGISTER_ENCDEC (TEXT,              text);
> +    REGISTER_DECODER(TEXTST,            textst);
>      REGISTER_DECODER(VPLAYER,           vplayer);
>      REGISTER_ENCDEC (WEBVTT,            webvtt);
>      REGISTER_ENCDEC (XSUB,              xsub);
> @@ -704,6 +705,7 @@ void avcodec_register_all(void)
>      REGISTER_PARSER(RV40,               rv40);
>      REGISTER_PARSER(SIPR,               sipr);
>      REGISTER_PARSER(TAK,                tak);
> +    REGISTER_PARSER(TEXTST,             textst);
>      REGISTER_PARSER(VC1,                vc1);
>      REGISTER_PARSER(VORBIS,             vorbis);
>      REGISTER_PARSER(VP3,                vp3);
> diff --git a/libavcodec/textst_parser.c b/libavcodec/textst_parser.c
> new file mode 100644
> index 0000000..5079a96
> --- /dev/null
> +++ b/libavcodec/textst_parser.c
> @@ -0,0 +1,49 @@
> +/*
> + * This file is part of FFmpeg.
> + *
> + * FFmpeg is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; either
> + * version 2.1 of the License, or (at your option) any later version.
> + *
> + * FFmpeg is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> + * Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with FFmpeg; if not, write to the Free Software
> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
> + */
> +
> +/**
> + * @file
> + * HDMV TextST subtitle parser
> + */
> +
> +#include "libavutil/intreadwrite.h"
> +#include "parser.h"
> +
> +static int textst_parse(AVCodecParserContext *s1, AVCodecContext *avctx,
> +                        const uint8_t **poutbuf, int *poutbuf_size,
> +                        const uint8_t *buf, int buf_size)
> +{
> +    if (buf_size > 13) {
> +        int64_t end;
> +
> +        s1->pts = ((int64_t)(buf[3] & 1) << 32) | AV_RB32(&buf[4]);
> +        end = ((int64_t)(buf[8] & 1) << 32) | AV_RB32(&buf[9]);
> +        s1->duration = (end - s1->pts);
> +    }
> +
> +    /* always return the full packet. this parser isn't doing any splitting or
> +       combining, only packet analysis */
> +    *poutbuf      = buf;
> +    *poutbuf_size = buf_size;
> +    return buf_size;
> +}
> +
> +AVCodecParser ff_textst_parser = {
> +    .codec_ids      = { AV_CODEC_ID_HDMV_TEXT_SUBTITLE },
> +    .parser_parse   = textst_parse,
> +};

Why does it need to be in a parser, instead of the demuxer? It seems
like this codec exists only in .ts anyway, and the way PTS/duration is
extracted seems very closely tied to the format.

> diff --git a/libavcodec/textstdec.c b/libavcodec/textstdec.c
> new file mode 100644
> index 0000000..a259d2d
> --- /dev/null
> +++ b/libavcodec/textstdec.c
> @@ -0,0 +1,108 @@
> +/*
> + * HDMV TextST decoder
> + * Copyright (c) 2017 Paul B Mahol
> + *
> + * This file is part of FFmpeg.
> + *
> + * FFmpeg is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; either
> + * version 2.1 of the License, or (at your option) any later version.
> + *
> + * FFmpeg is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> + * Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with FFmpeg; if not, write to the Free Software
> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
> + */
> +
> +#include <string.h>
> +
> +#include "libavutil/bprint.h"
> +#include "avcodec.h"
> +#include "ass.h"
> +#include "bytestream.h"
> +
> +static int textst_event_to_ass(AVBPrint *buf, const char *p, int size)
> +{
> +    GetByteContext gb;
> +    int i, count;
> +
> +    bytestream2_init(&gb, p, size);
> +    count = bytestream2_get_byte(&gb);
> +
> +    if (count > 127) {
> +        int size = bytestream2_get_be16(&gb);
> +        bytestream2_skip(&gb, size);
> +    }
> +    if (bytestream2_get_bytes_left(&gb) > 2) {
> +        count = bytestream2_get_byte(&gb);
> +
> +        for (i = 0; i < count; i++) {
> +            int dlength;
> +
> +            bytestream2_skip(&gb, 2);
> +            dlength = bytestream2_get_be16(&gb);
> +
> +            while (dlength > 3) {
> +                int type, length;
> +                int code = bytestream2_get_byte(&gb);
> +
> +                dlength--;
> +                if (code != 0x1b)
> +                    continue;
> +
> +                type   = bytestream2_get_byte(&gb);
> +                length = bytestream2_get_byte(&gb);
> +                dlength -= (2 + length);
> +
> +                switch (type) {
> +                case 1:
> +                    av_bprint_append_data(buf, gb.buffer, FFMIN(length, bytestream2_get_bytes_left(&gb)));
> +                    bytestream2_skip(&gb, length);
> +                    break;
> +                case 0x0a:
> +                    av_bprintf(buf, "\n");
> +                default:
> +                    bytestream2_skip(&gb, length);
> +                    break;
> +                }
> +            }
> +        }
> +    }
> +
> +    return 0;
> +}
> +
> +static int textst_decode_frame(AVCodecContext *avctx,
> +                               void *data, int *got_sub_ptr, AVPacket *avpkt)
> +{
> +    FFASSDecoderContext *s = avctx->priv_data;
> +    const char *ptr = avpkt->data;
> +    AVSubtitle *sub = data;
> +    AVBPrint buf;
> +    int ret = 0;
> +
> +    av_bprint_init(&buf, 0, AV_BPRINT_SIZE_UNLIMITED);
> +    if (ptr && avpkt->size > 13 && !textst_event_to_ass(&buf, ptr + 13, avpkt->size - 13))
> +        ret = ff_ass_add_rect(sub, buf.str, s->readorder++, 0, NULL, NULL);
> +    av_bprint_finalize(&buf, NULL);
> +    if (ret < 0)
> +        return ret;
> +    *got_sub_ptr = sub->num_rects > 0;
> +    return avpkt->size;
> +}
> +
> +AVCodec ff_textst_decoder = {
> +    .name           = "textst",
> +    .long_name      = NULL_IF_CONFIG_SMALL("HDMV TextST subtitle"),
> +    .type           = AVMEDIA_TYPE_SUBTITLE,
> +    .id             = AV_CODEC_ID_HDMV_TEXT_SUBTITLE,
> +    .decode         = textst_decode_frame,
> +    .init           = ff_ass_subtitle_header_default,
> +    .flush          = ff_ass_decoder_flush,
> +    .priv_data_size = sizeof(FFASSDecoderContext),
> +};
> diff --git a/libavformat/utils.c b/libavformat/utils.c
> index 0711310..74f808f 100644
> --- a/libavformat/utils.c
> +++ b/libavformat/utils.c
> @@ -1445,6 +1445,7 @@ static int parse_packet(AVFormatContext *s, AVPacket *pkt, int stream_index)
>  
>          out_pkt.stream_index = st->index;
>          out_pkt.pts          = st->parser->pts;
> +        out_pkt.duration     = st->parser->duration;
>          out_pkt.dts          = st->parser->dts;
>          out_pkt.pos          = st->parser->pos;
>  

This overwrites values written to out_pkt.duration above this code.
Does it even pass FATE?


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